The production of colibacillosis in turkeys following sequential exposure to Newcastle disease virus or Bordetella avium, avirulent hemorrhagic enteritis virus, and Escherichia coli.
Female large white turkeys were inoculated intranasally with either Newcastle disease virus (ND) or B. avium (BA) at 4 weeks of age. This was followed by oral inoculation with an avirulent (vaccine) strain of haemorrhagic enteritis virus (HE) at 5 weeks and i.v. inoculation with E. coli (EC) at 6 weeks. Control birds received ND, BA, or HE followed by EC; EC alone; or kept as uninfected controls. Turkeys receiving one agent before EC challenge showed no significant increase in mortality or pericarditis. Those exposed to ND or BA followed by HE and EC showed significant increase in mortality and pericarditis. A highly significant positive correlation between the number of infectious agents encountered during primary exposure and the incidence of colibacillosis after EC challenge was demonstrated.